The Poultry Red Mite, Dermanyssus gallinae, travels far but not frequently, and takes up permanent residence on farms.

Management of Dermanyssus gallinae, a cosmopolitan hematophagous mite responsible for damage in layer poultry farming, is hampered by a lack of knowledge of its spatio-temporal population dynamics. Previous studies have shown that the circulation of this pest between farms is of strictly anthropogenic origin, that a mitochondrial haplogroup has been expanding on European farms since the beginning of the 21st century and that its local population growth may be particularly rapid. To refine our understanding of how D. gallinae spreads within and among farms, we characterized the genetic structure of mite populations at different spatial scales and sought to identify the main factors interrupting gene flow between poultry houses and between mitochondrial haplogroups. To this end, we selected and validated the first set of nuclear microsatellite markers for D. gallinae and sequenced a region of the CO1-encoding mitochondrial gene in a subsample of microsatellite-genotyped mites. We also tested certain conditions required for effective contamination of a poultry house through field experimentation, and conducted a survey of practices during poultry transfers. Our results confirm the role of poultry transport in the dissemination of mite populations, but the frequency of effective contamination after the introduction of contaminated material into poultry houses seems lower than expected. The high persistence of mites on farms, even during periods when poultry houses are empty and cleaned, and the very large number of nodes in the logistic network (large number of companies supplying pullets or transporting animals) undoubtedly explain the very high prevalence on farms. Substantial genetic diversity was measured in farm populations, probably as a result of the mite's known haplodiploid mode of sexual reproduction, coupled with the dense logistic network. The possibility of the occasional occurrence of asexual reproduction in this sexually reproducing mite was also revealed in our analyses, which could explain the extreme aggressiveness of its demographic dynamics under certain conditions.

Measuring behaviour in hens using an ethogram to assess analgesia during further refinement of a high welfare, on-hen, poultry red mite feeding device.

Background: To refine an on-hen mite feeding device, an ethogram was employed to measure the reactions of hens during a routine experimental procedure (feather plucking) and to assess effects of analgesic cream on those reactions. Methods: Three experimental groups were used; one treated with EMLA 5% before plucking ("EMLA group"); one with aqueous cream ("placebo group") and a "no treatment" group. Behaviours were measured and compared on three days: 'dummy handling day' i.e. no plucking; 'plucking day', plucking the left thigh; and 'treatment day' i.e with right thighs plucked post-treatment. Poultry red mite feeding assays were performed to examine effect of creams on mite feeding rates, mortality and fecundity. All data were analysed using generalised linear (mixed) modelling approaches. Results: Use of the ethogram demonstrated no significant difference in hen behaviours in the EMLA group between dummy handling day and treatment day (p = 0.949) alongside a significant reduction in measured behaviours between plucking day and treatment day in the same group (p = 0.028). There was a statistically significant increase in measured behaviours from the dummy handling day to the plucking day in both placebo (p = 0.011) and no treatment group (p < 0.001). Effect sizes and directions were similar between dummy handling and treatment days in the 'placebo' and 'no treatment' groups, though not statistically significant (placebo, p = 0.064; no treatment p = 0.069). Mite feeding in the EMLA group was significantly lower than in the no treatment group in feeding assay 1 (p = 0.029) only. Mite mortality and fertility were unaffected. Conclusions: The ethogram successfully measured changes in observed behaviours between the dummy handling session and procedures. No adverse effects of EMLA cream on hens were demonstrated at 3mg/kg in hens. Use of analgesia for this routine procedure improves hens' experiences during experimental trials.

Immunity to Haemonchus contortus and Vaccine Development.

Sheep are capable of developing protective immunity to Haemonchus contortus through repeated exposure to this parasite, although this immune protection is the result of a complex interaction among age, gender, physiological status, pregnancy, lactation, nutrition and innate and adaptive immunity in the host animal. There are multiple effectors of the protective immune response, which differ depending on the developmental stage of the parasite being targeted, and our understanding of the effector mechanisms has developed considerably in the 2000s. The rational design of vaccines based on 'natural' or 'exposed' antigens depends on an understanding of this exposure-induced immunity. However, the most effective current vaccines rely on protection via the induction of high circulating antibody levels to 'hidden' gut antigens of H. contortus. The success of this latter strategy has resulted in the launch of a vaccine, which is based on extracts of the parasite's gut, to aid in the control of Haemonchus in Australia. The development of recombinant subunit vaccines based on the components of the successful native vaccine has not yet been achieved and most of the recent successes with recombinant subunit vaccines have focussed on antigens unrelated to the gut antigens. The future integration of an understanding of the immunobiology of this parasite with advances in antigen identification, expression (or synthesis) and presentation is likely to be pivotal to the further development of these recombinant subunit vaccines. Recent progress in each of the components underpinning this integrated approach is summarized in this review.

Molecular approaches to differentiate three species of Nematodirus in sheep and goats from China based on internal transcribed spacer rDNA sequences.

Internal transcribed spacer (ITS) rDNA sequences of three Nematodirus species from naturally infected goats or sheep in two endemic provinces of China were analysed to establish an effective molecular approach to differentiate Nematodirus species in small ruminants. The respective intra-specific genetic variations in ITS1 and ITS2 rDNA regions were 0.3-1.8% and 0-0.4% in N. spathiger, 0-6.5% and 0-5.4% in N. helvetianus, and 0-4.4% and 0-6.1% in N. oiratianus from China. The respective intra-specific variations of ITS1 and ITS2 were 1.8-4.4% and 1.6-6.1% between N. oiratianus isolates from China and Iran, 5.7-7.1% and 6.3-8.3% between N. helvetianus samples from China and America. For N. spathiger, compared with samples from China, sequence differences in ITS1 rDNA were 0.3-2.4% in isolates from America, 0.3-2.9% in New Zealand and 2.1-2.4% in Australia. Genetic variations in ITS2 rDNA of N. spathiger were 0-0.4% between samples from China and America, and 0-0.8% between samples from China and New Zealand. Using mutation sites, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and specific PCR techniques were developed to differentiate these three Nematodirus species. The specific PCR assay allowed the accurate identification of N. oiratianus from other common nematodes with a sensitivity of 0.69 pg and further examination of Nematodirus samples demonstrated the reliability of these two molecular methods.

RNA interference for the identification of ectoparasite vaccine candidates.

Ectoparasites present a major challenge for disease management globally. With drug resistance increasingly observed in many disease-causing species, the need for novel control measures is pressing. Ever-expanding genomic resources from 'next generation' sequencing are now available for a number of arthropod ectoparasites, necessitating an effective means of screening these data for novel candidates for vaccine antigens or targets for chemotherapeutics. Such in vitro screening methods must be developed if we are to make discoveries in a timely and cost-effective manner. This review will discuss the potential that RNA interference (RNAi) has demonstrated thus far in the context of arthropod ectoparasites and the potential roles for this technology in the development of novel methods for parasite control.

Characterization of Trichuris trichiura from humans and T. suis from pigs in China using internal transcribed spacers of nuclear ribosomal DNA.

Trichuris trichiura and Trichuris suis parasitize (at the adult stage) the caeca of humans and pigs, respectively, causing trichuriasis. Despite these parasites being of human and animal health significance, causing considerable socio-economic losses globally, little is known of the molecular characteristics of T. trichiura and T. suis from China. In the present study, the entire first and second internal transcribed spacer (ITS-1 and ITS-2) regions of nuclear ribosomal DNA (rDNA) of T. trichiura and T. suis from China were amplified by polymerase chain reaction (PCR), the representative amplicons were cloned and sequenced, and sequence variation in the ITS rDNA was examined. The ITS rDNA sequences for the T. trichiura and T. suis samples were 1222-1267 bp and 1339-1353 bp in length, respectively. Sequence analysis revealed that the ITS-1, 5.8S and ITS-2 rDNAs of both whipworms were 600-627 bp and 655-661 bp, 154 bp, and 468-486 bp and 530-538 bp in size, respectively. Sequence variation in ITS rDNA within and among T. trichiura and T. suis was examined. Excluding nucleotide variations in the simple sequence repeats, the intra-species sequence variation in the ITS-1 was 0.2-1.7% within T. trichiura, and 0-1.5% within T. suis. For ITS-2 rDNA, the intra-species sequence variation was 0-1.3% within T. trichiura and 0.2-1.7% within T. suis. The inter-species sequence differences between the two whipworms were 60.7-65.3% for ITS-1 and 59.3-61.5% for ITS-2. These results demonstrated that the ITS rDNA sequences provide additional genetic markers for the characterization and differentiation of the two whipworms. These data should be useful for studying the epidemiology and population genetics of T. trichiura and T. suis, as well as for the diagnosis of trichuriasis in humans and pigs.

Comparative characterization of microRNA profiles of different genotypes of Toxoplasma gondii.

The present study compared the miRNA expression profiles of five Toxoplasma gondii strains, namely RH (Type I, ToxoDB10), TgXD (Type I, ToxoDB10), PRU (Type II, ToxoDB1), QHO (Type II, ToxoDB1) and TgC7 (ToxoDB9), by Solexa deep sequencing, bioinformatics analysis and real-time quantitative PCR. A total of 7, 15, 10, 12 and 10 miRNAs were found from RH, TgXD, PRU, QHO and TgC7 strains, respectively. Thirteen miRNAs were shared by three genotypes, with only one miRNA shared by all of the 5 strains and others shared by 2 or more strains. A large number of targets ranging from 1 to 185 were identified for commonly shared miRNAs and strain-specific miRNAs with complete or nearly complete complementarity. Functional prediction showed that these targets were mostly focused on catalytic activity (191 targets) and binding activity (183 targets). Nonetheless, the majority of targets and most of the miRNAs are related to the virulence or invasion proteins of different strains of T. gondii, including ROP and MIC, as well as some other proteins, such as AMA1, GRA and RHO. The present study characterized comparatively the miRNA profiles of 3 different genotypes of T. gondii, identified genotype-shared miRNAs and strain-specific miRNAs.

Seroprevalence of Toxoplasma gondii and Neospora caninum infection in dairy cows in subtropical southern China.

Toxoplasma gondii and Neospora caninum are closely related protozoan parasites which cause lowered production and increased abortion in dairy cows. The aim of the present study was to determine the seroprevalence of T. gondii and N. caninum infection in dairy cows in the Guangxi Zhuang Autonomous Region (GZAR), subtropical southern China. In total, 875 serum samples were collected from the tail veins of dairy cows in 6 main dairy cow-rearing districts of 4 administrative cities in GZAR. The samples were surveyed for T. gondii antibody using the Indirect Haemagglutination Test (IHA), and 365 of the serum samples were examined for N. caninum antibody by indirect Enzyme-Linked Immunosorbent Assay (ELISA). The overall seroprevalence of T. gondii in dairy cows was 13·71% (120/875), and the average seroprevalence of N. caninum was 15·07% (55/365). There were significant differences in the seroprevalence of N. caninum infection between different districts (P = 0·002, χ 2 = 9·261). The highest prevalences of T. gondii and N. caninum were found in cows older than 8 years and those that had completed 5-6 pregnancies. Five cows (1·37%) presented antibodies against both T. gondii and N. caninum, and dairy cows with both T. gondii and N. caninum antibodies had higher abortion rates. The present results indicate widespread exposure of dairy cows to T. gondii and N. caninum in GZAR, subtropical southern China.

Phage-display library biopanning as a novel approach to identifying nematode vaccine antigens.

Infections with parasitic nematodes are of significant welfare and economic importance worldwide, and because of the emergence of anthelmintic resistance, this has lead to alternative methods of parasite control being required. Vaccination offers a feasible alternative control, and the majority of research has focused on the production of recombinant versions of native antigens previously identified as protective in vaccinated animals. Attempts at the production of protective recombinant subunit vaccines have been hindered, however, as these antigens have invariably failed to replicate the same level of protective immune response as seen with the native versions. It has been proposed that these failures are owing to the fact that the recombinant proteins do not contain the appropriate post-translational modifications to retain the protective capacity of the native molecules. In this review, we discuss a novel approach to vaccine antigen identification through the application of random peptide phage-display libraries and their use to identify peptide sequences that potentially mimic the structure(s) of antigenic epitopes. This area of research is still relatively novel with respect to parasites, and the current state of the art will be discussed here.

A calcium-activated apyrase from Teladorsagia circumcincta: an excretory/secretory antigen capable of modulating host immune responses?

A cDNA representing the gene Teladorsagia circumcincta apyrase-1 (Tci-apy-1) was isolated, by PCR, from a T. circumcincta fourth-stage larval (L4) cDNA library. The closest orthologue of this gene is a Ca(2+)-dependent apyrase from Ostertagia ostertagi, with 92% amino acid identity across all 339 residues. Tci-apy-1 is transcribed in a stage-specific manner, the transcript being predominant in L4, detectable in the adult cDNA, but absent from eggs and infective third-stage larvae (L3). The protein, Tci-APY-1, was detected by immunoblotting in extracts of L4 nematodes and was present in excretory/secretory products from the same developmental stage. A recombinant version of Tci-APY-1 was expressed in bacteria as an active enzyme that hydrolysed nucleoside triphosphate substrates with a preference of ATP over other nucleoside triphosphates. Recombinant Tci-APY-1 hydrolysed ATP and ADP but not AMP. Apyrase activity was divalent cation-dependent, with no hydrolysis in the presence of Mg(2+), but activation in the presence of Ca(2+). Recombinant Tci-APY-1 was bound by IgG present in serum and both IgG and IgA present in abomasal mucus from trickle-infected, immune sheep but not in material derived from lambs exposed to a single infection. The potential immunomodulatory roles of this Tci-APY-1 are discussed in relation to purinergic signalling.

Using lectins to identify hidden antigens in Fasciola hepatica.

Fasciola hepatica is the causative agent of fascioliasis, one of the most economically important helminth diseases of livestock worldwide. Traditionally, fascioliasis has been controlled by the strategic use of fasciolicidal drugs, but the emergence of resistant parasites has spurred an interest in developing vaccines as an alternative means of control. Most vaccine studies to date have evaluated conventional antigens, which are exposed to the host's immune system during the course of a natural infection. 'Hidden' antigens have proven to be effective vaccine candidates in other parasite species, most notably the blood-feeding nematode parasite, Haemonchus contortus, and tend to be expressed in the intestine or gut of the parasite. Fasciola hepatica is known to ingest large quantities of blood and may be vulnerable to this approach. Most, if not all, of the candidate antigens identified thus far have been membrane-bound glycoproteins which were solubilized by detergents. Here, we have attempted to employ lectins to select gut-associated glycoproteins from complex mixtures of somatic extracts of adult F. hepatica. We have conducted a comprehensive lectin-binding screen on adult histological sections with a panel of 16 fluorescently labelled lectins. Seven of the lectins bound to molecules within the gastrodermis but also bound to a range of other tissues. Within the gut tissues, jacalin and peanut lectins bound selectively to the gut lamellae and gastrodermal cells, respectively. These lectins were then used to isolate proteins from the integral membrane protein component of the adult fluke. Both lectins showed selectivity for relatively simple subsets of proteins compared to the original crude extracts.

A calcium-activated nucleotidase secreted from Ostertagia ostertagi 4th-stage larvae is a member of the novel salivary apyrases present in blood-feeding arthropods.

Apyrases (ATP-diphosphohydrolase) comprise a ubiquitous class of glycosylated nucleotidases that hydrolyse extracellular ATP and ADP to orthophosphate and AMP. One class of newly-described, Ca2+-dependent, salivary apyrases known to counteract blood-clotting, has been identified in haematophagous arthropods. Herein, we have identified a gene (Oos-apy-1) encoding a protein that structurally conforms to the Ca2+-activated apyrase from the bed bug, Cimex lectularius, by immunologically screening an Ostertagia L4 cDNA expression library. The expressed protein (rOos-APY-1) was biochemically functional in the presence of Ca2+ only, with greatest activity on ATP, ADP, UTP and UDP. Host antibodies to the fusion protein appeared as early as 14 days post-infection (p.i.) and increased through 30 days p.i. Immunohistochemical and Western blot analyses demonstrated that the native Oos-APY-1 protein is present in the glandular bulb of the oesophagus and is confined to the L4. A putative signal sequence at the N-terminus and near 100% identity with a Teladorsagia circumcincta L4 secreted protein is consistent with the native protein being secreted at the cellular level. Predicated upon substrate specificity, the native protein may be used by the parasite to control the levels of host extracellular nucleotides released by locally-damaged tissues in an effort to modulate immune intervention and inflammation.

A macrophage migration inhibitory factor-like tautomerase from Teladorsagia circumcincta (Nematoda: Strongylida).

A macrophage migration inhibitory factor (MIF)-like molecule, Tci-MIF-1, was isolated from Teladorsagia circumcincta and subjected to detailed characterization. A cDNA representing Tci-mif-1 was isolated following its identification in third-stage larvae (L3)-enriched cDNA population. Sequencing of the cDNA indicated a 348-bp open reading frame (ORF) with the closest orthologue being a MIF derived from the human hookworm Ancylostoma ceylanicum. Messenger RNA (mRNA) representing the Tci-MIF-1 transcript was detected in eggs, L3 and adult stages of T. circumcincta. The transcript was also present, but to a lesser extent in fourth-stage larvae (L4). Detection of Tci-MIF-1 protein in T. circumcincta developmental stages reflected the transcript levels identified by reverse transcriptase-PCR. Using immunohistochemistry, the Tci-MIF-1 protein was shown to have a diffuse distribution in L3 tissue, and in L4 and adult stages, the protein was localized to the nematode gut. A recombinant version of Tci-MIF-1 was produced, and enzymic assays indicated that this recombinant protein and a somatic extract of L3 possessed dopachrome tautomerase activity as has been observed previously in other MIF-like molecules. Neither native, purified Tci-MIF nor recombinant Tci-MIF-1 dramatically influenced the in vitro migration of sheep monocytes.

Teladorsagia circumcincta: activation-associated secreted proteins in excretory/secretory products of fourth stage larvae are targets of early IgA responses in infected sheep.

A detailed proteomic analysis of excreted/secretory (ES) proteins derived from fourth stage larvae (L4) of Teladorsagia circumcincta identified a number of components, including N-type and C-type single domain activation-associated secreted proteins (ASPs). Immunoblotting of L4 ES extracts with abomasal mucus derived from infected, immune sheep demonstrated the immunogenicity of some of these components, including an N-type single-domain ASP, designated Tci-ASP-1. The full-length cDNA encoding this protein was isolated and sequenced. Homology searches using the inferred amino acid sequence of Tci-ASP-1 showed that it had highest identity (75% over 231 residues) to, a N-type, single-domain ASP from Ostertagia ostertagi. Phylogenetic analysis confirmed the relationship of Tci-ASP-1 with other N-type ASPs. Reverse-transcriptase (RT)-PCR experiments demonstrated the presence of transcript encoding Tci-ASP-1 in L4 and adult stage T. circumcincta but not in pre-parasitic stages such as eggs and third stage larvae. A recombinant version of Tci-ASP-1 was expressed in Escherichia coli and the purified protein was reactive with IgA present in abomasal mucus derived from immune sheep.

daf-7-related TGF-beta homologues from Trichostrongyloid nematodes show contrasting life-cycle expression patterns.

The transforming growth factor-beta (TGF-beta) gene family regulates critical processes in animal development, and plays a crucial role in regulating the mammalian immune response. We aimed to identify TGF-beta homologues from 2 laboratory model nematodes (Heligmosomoides polygyrus and Nippostrongylus brasiliensis) and 2 major parasites of ruminant livestock (Haemonchus contortus and Teladorsagia circumcincta). Parasite cDNA was used as a template for gene-specific PCR and RACE. Homologues of the TGH-2 subfamily were isolated, and found to differ in length (301, 152, 349 and 305 amino acids respectively), with variably truncated N-terminal pre-proteins. All contained conserved C-terminal active domains (>85% identical over 115 amino acids) containing 9 cysteine residues, as in C. elegans DAF-7, Brugia malayi TGH-2 and mammalian TGF-beta. Surprisingly, only the H. contortus homologue retained a conventional signal sequence, absent from shorter proteins of other species. RT-PCR assays of transcription showed that in H. contortus and N. brasiliensis expression was maximal in the infective larval stage, and very low in adult worms. In contrast, in H. polygyrus and T. circumcincta, tgh-2 transcription is higher in adults than infective larvae. The molecular evolution of this gene family in parasitic nematodes has diversified the pre-protein and life-cycle expression patterns of TGF-beta homologues while conserving the structure of the active domain.

Molecular characterization, expression and localization of a peroxiredoxin from the sheep scab mite, Psoroptes ovis.

The sheep scab mite, Psoroptes ovis, induces an intensely pruritic exudative dermatitis which is responsible for restlessness, loss of appetite and weight loss. Within the first 24 h of infection, there is a rapid inflammatory influx of eosinophils and apoptosis of the keratinocytes at the site of infection. The former cell type is capable of a sustained respiratory burst, toxic products of which may directly damage the mite and also contribute to lesion formation. Analysis of a P. ovis expressed sequence tag (EST) database identified a number of antioxidant enzyme-encoding sequences, including peroxiredoxin (thioredoxin peroxidase EC 1.11.1.15), all of which may help the mite endure the potentially toxic skin environment. A full length sequence encoding Po-TPx, a protein of 206 amino acids which showed high homology to a peroxiredoxin from the salivary gland of the tick Ixodes scapularis, was amplified from P. ovis cDNA. Recombinant Po-TPx was expressed in bacteria and antiserum to this protein was used to localize native Po-TPx in mite sections. Peroxiredoxin was localized, amongst other sites, to a subpharyngeal region in mite sections. The recombinant protein was recognized by sera from sheep infested with the mite suggesting that it may be secreted or excreted by the mite and interact with the host immune response.

A portrait of the "SCP/TAPS" proteins of eukaryotes--developing a framework for fundamental research and biotechnological outcomes.

A wide range of proteins belonging to the SCP/TAPS "family" has been described for various eukaryotic organisms, including plants and animals (vertebrates and invertebrates, such as helminths). Although SCP/TAPS proteins have been proposed to play key roles in a number of fundamental biological processes, such as host-pathogen interactions and defence mechanisms, there is a paucity of information on their genetic relationships, structures and functions, and there is no standardised nomenclature for these proteins. A detailed analysis of the relationships of members of the SCP/TAPS family of proteins, based on key protein signatures, could provide a foundation for investigating these areas. In this article, we review the current state of knowledge of key SCP/TAPS proteins of eukaryotes, with an emphasis on those from parasitic helminths, and undertake a comprehensive, systematic phylogenetic analysis of currently available full-length protein sequence data (considering characteristic protein signatures or motifs) to infer relationships and provide a framework (based on statistical support) for the naming of these proteins. This framework is intended to guide genomic and molecular biological explorations of key SCP/TAPS molecules associated with infectious diseases of plants and animals. In particular, fundamental investigations of these molecules in parasites and the integration of structural and functional data could lead to new and innovative approaches for the control of parasitic diseases, with important biotechnological outcomes.

Proteomic analysis of excretory/secretory products released by Teladorsagia circumcincta larvae early post-infection.

Teladorsagia circumcincta is an important parasitic nematode of domestic small ruminants. Drug resistance in this species is common so alternative methods of control are required. As animals develop immunity to T. circumcincta, vaccination is a valid option. Little is known about the antigens that play a role in stimulating immunity at this host/parasite interface. As responses generated between 1 and 5 dpi are known to affect development of these nematodes in their gastric niche, we focused on proteins released during the early stages of infection. To identify molecules potentially involved in immunity, we undertook a proteomics analysis of proteins released from larvae harvested at 1-, 3- and 5-days post-infection (dpi). This analysis produced peptide sequence data that was used to search information available in T. circumcincta expressed sequence tag (EST) databases and enabled identification of a number of excretory/secretory (ES) proteins. Immunoblots were performed to assess the relative molecular weight of ES antigens that were targets of local IgA responses in mucus from sheep rendered immune to infection. ELISA was performed to assess antigen-specific mucus IgA levels in individual sheep. These experiments provided preliminary evidence that the proteins identified in the larval secretome were subject to these antibody responses.

Immune recognition of the surface associated antigen, Tc-SAA-1, from infective larvae of Teladorsagia circumcincta.

A cDNA encoding a surface-associated antigen was amplified by reverse transcriptase polymerase chain reaction (PCR) from RNA extracted from Teladorsagia circumcincta exsheathed third stage larvae (xL3). The protein encoded by this cDNA, Tc-SAA-1, displays 77% identity over 162 amino acid residues to a surface associated antigen from Ancylostoma caninum (Ac-SAA-1). Antiserum raised against a bacterially-expressed recombinant form of Tc-SAA-1 reacted with a native protein in somatic and surface extracts of xL3 but not with L4 or adult parasites. Limited binding of anti-Tc-SAA-1 antibody was observed on the cuticular surface of xL3 s, however, regions of localization underlying the cuticle were observed. Incubation of xL3 T. circumcincta with anti-SAA rabbit serum failed to significantly inhibit penetration of the abomasal mucosa in vitro. IgA in abomasal mucus derived from sheep that had received a trickle infection of T. circumcincta bound recombinant Tc-SAA-1.